1. Field of the Invention
The present invention is generally related to a marine propulsion device with a fuel system and a fuel system cooler and, more particularly, to a marine fuel system that incorporates a Peltier-effect cooling unit to reduce the temperature of fuel as it passes between a fuel storage reservoir, a fuel pumping module, and the engine of the marine propulsion device.
2. Description of the Prior Art
Peltier-effect devices were conceived in 1834. The Peltier-effect occurs whenever current passes through the circuit of two dissimilar conductors. Depending on the direction of the current, this junction of the two conductors will either absorb or release heat. The amount of heat provided is in direct proportion to the current supply. A Peltier-effect device, sometimes referred to as a thermoelectric cooling system, provides a cold junction where energy, in the form of heat, is absorbed by electrons as they pass from a low energy level in a P-type semiconductor element to a higher energy level in a N-type semiconductor element. A power supply provides the energy to move the electrons through the system. At the hot junction, energy is expelled to a heat sink as electrons move from a high energy level N-type element to a low energy level P-type element. Thermoelectric cooling components are made from two elements of the semiconductor, primarily bismuth telluride, which are heavily doped to create either an excess (N-type component) or deficiency (P-type component) of electrons. Heat absorbed at the cold junction is pumped to the hot junction at a rate proportional to current passing through the circuit and the number of cooling couples incorporated in the device.
U.S. Pat. No. 3,564,860, which issued to Reich et al. on Feb. 23, 1971, describes thermoelectric elements utilizing distributed Peltier-effect. A thermoelectric couple for use in a Peltier cooling device includes P-type and N-type thermoelectric elements in which at least one of the thermoelectric elements is formed of a material having varying thermoelectric properties. The Seebeck coefficient (absolute value) of the material adjacent the cold junction is significantly less than the Seebeck coefficient (absolute value) of material adjacent the hot junction. The variance in such properties may be a continuous gradient, or the thermoelectric elements may be made up of discrete segments of different materials bonded together.
U.S. Pat. No. 3,635,037, which issued to Hubert on Jan. 18, 1972, describes a Peltier-effect heat pump. A Peltier-effect pile is mounted in a heat exchanger or heat sink with semi-conductive barrier layers insulating the Peltier electrodes from the metal of the heat sink. The semi-conductive layers are poled electrically or biased to minimize electrical conductivity thereacross but permit maximum heat flow between the Peltier pile and the heat exchange jacket.
U.S. Pat. No. 5,174,266, which issued to Evdokimo on Dec. 29, 1992, describes a fuel temperature control device with thermoelectric modules. The device maintains fuel at a programmable temperature by adding heat to or drawing heat from the fuel as it passes through a heat exchanger. The secondary heat exchanger is used in conjunction with Peltier-effect thermoelectric modules to perform the addition or extraction of heat. A control unit receives fuel temperature signals and generates module electrical control signals to control the amount and direction of heat transfer.
U.S. Pat. No. 6,067,970, which issued to Awarzamani et al. on May 30, 2000, describes a fuel injection device for an internal combustion engine. The device has a fuel injection valve which sprays the fuel in the direction of an inlet valve and includes an electric heating element for the fuel before it reaches an inlet valve. The fuel injection device has a fuel injection valve which sprays the fuel in the form of a fuel jet in the direction of the inlet valve of the internal combustion engine, the fuel jet leaving the fuel injection valve at least in part strikes an electric heating element which, according to the invention, is designed as a Peltier element. The fuel injection device according to the invention is intended, in particular, for mixture-compressing, applied-ignition internal combustion engines.
U.S. Pat. No. 5,915,626, which issued to Awarzamani et al. on Jun. 29, 1999, describes a fuel injector that includes a magnetic coil whose power dissipation is utilized to pre-heat fuel flowing through the fuel injector. The magnetic coil is arranged so that a thermal coupling between the magnetic coil and the fuel flowing through a heat exchanger segment is acquired. In addition, a Peltier element can be arranged between the magnetic coil and the heat exchanger segment. Furthermore, the fuel can also be heated using a heating coil.
U.S. Pat. No. 6,253,742, which issued to Wickman et al. on Jul. 3, 2001, discloses a fuel supply method for a marine propulsion engine. It is a method for controlling the operation of a fuel system of an outboard motor using a lift pump to transfer fuel from a remote tank to a vapor separator tank. Only one level sensor is provided in the vapor separator tank and an engine control unit monitors the total fuel usage subsequent to the most recent filling of the tank. When the fuel usage indicates that the fuel level in the vapor separator tank has reached a predefined lower level, a lift pump is activated to draw fuel from a remote tank and provide that fuel to the vapor separator tank.
U.S. Pat. No. 6,390,871, which issued to Wickman et al. on May 21, 2002, discloses a fuel reservoir mounted to a driveshaft housing of an outboard motor. A fuel system for a marine propulsion system includes a reservoir that defines a cavity in which first and second fuel pumps are disposed. The reservoir is mounted on the marine propulsion system at a location which causes the reservoir to be at least partially submerged within, and in thermal communication with, water in which the marine propulsion system is operated when a propulsor of the marine propulsion system is inactive. The first fuel pump is a lift pump which draws fuel from a fuel tank and pumps the fuel into the cavity of the reservoir. The second fuel pump is a high pressure pump which draws fuel from the cavity and pumps the fuel at a higher pressure to a fuel rail of an engine.
U.S. Pat. No. 6,527,603, which issued to Wickman et al. on Mar. 4, 2003, discloses a fuel delivery system for a marine propulsion device. The system includes a reservoir that defines a cavity in which first and second fuel pumps are disposed. The first fuel pump is a lift pump which draws fuel from a fuel tank and pumps the fuel into the cavity of the reservoir. The second fuel pump is a high pressure pump which draws fuel from the cavity and pumps the fuel at a higher pressure to a fuel rail of an engine.
U.S. Pat. No. 6,553,974, which issued to Wickman et al. on Apr. 29, 2003, discloses an engine fuel system with a fuel vapor separator and a fuel vapor vent canister. A fuel supply system for a marine engine provides an additional fuel chamber, associated with a fuel vapor separator, that receives fuel vapor from a vent of the fuel vapor separator. In order to prevent the flow of liquid fuel into and out of the additional fuel chamber, a valve is provided which is able to block the vent of the additional chamber. In addition, a sensor is provided to provide a signal that represents a condition in which liquid fuel within the additional fuel chamber exceeds a predetermined level.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Marine propulsion devices occasionally experience vapor lock conditions in which fuel vaporizes to a gaseous state and is difficult to pump from a fuel storage system to the engine. Various techniques have been used to cool the fuel in order to avoid this deleterious condition. It would be significantly beneficial if a simplified system could be provided to remove heat from the fuel in order to avoid this situation.